Compositions plasticized with esters of tris(carboxy)-hexahydrotriazines



United s cates Patent @hlice EJ73 399 Patented Mar. 16, 1965 Delaware No Drawing. Filed Nov. 20, 1961, Ser. No. 154,104 6 (Ilaims. (Cl. 106-176) This invention relates to novel plasticized compositions, and more particularly, to poly(vinyl chloride) and nitrocellulose compositions plasticized with esters of tris(carboxy) -hexahydrotriazines. This application is a continuation-in-part of copending application Serial No. 801,457, filed March 24, 1959, now Patent No. 3,065,232.

Heretofore it has been known to prepare lower alkyl tris(carbalkoxy)-hexahydrotriazines by the reaction of methyl, ethyl or propyl carbamates with aqueous formaldehyde, in the presence of an acid catalyst. For example, the preparation of tris(carbethoxy)-hexahydrotriazine by the reaction of urethane and forrnfldehyde in hydrochloric acid is described by C. S. Marvel in lour. Am. Chem. Soc. 68, 1685 (1946). However, when the carbamate re actant is derived from alcohols higher than propyl, the product of this reaction is not a simple hexahydrotriazine as before, but is a viscous oil or waxy solid, usually having a viscosity in the range of about 10 to 2000 poises. The viscosity of the polymers obtained depends on the duration of the reaction between the carbamate and formaldehyde: the longer the reaction time, the higher the product viscosity. Only from lower alkyl carbamates are crystallizable tris(carball oxy)-hexahydrotriazines produced, and even this may not happen if the reaction mixture is subjected to prolonged heating, but viscous polymeric products may be produced instead. No cyclic triazines have been obtained from this reaction when the starting material is a carbamate derived from alcohols higher than propyl, and in fact the propyl compound is obtainable only under carefully controlled conditions. monomeric esters of tris(carboxy)-hexahydrotriazines derived from carbamates higher than propyl have heretofore not been known, since known methods of preparing such compounds resulted in the formation of polymers rather than monomers; these polymeric products are described in US. Patent 2,171,965.

It has now been discovered that the high molecular Weight polymeric oils and solids which, as reported in the prior art, are produced by reacting carbamates higher than propyl with formaldehyde, can be transformed into monomeric cyclic hexahydrotriazines, by heating the polymers with an acid catalyst at temperatures above 100' C. in the substantial absence of water. The monoeric hexahydrotn'azines are produced in good yields by what is, in effect, a degradation and rearrangement of the linear polymera reaction which does not occur to a significant extent except under the anhydrous conditions imposed after the polymer has formed. The cyclic hexahydrotriazines thus produced are low-viscosity, oily liquids, having a utility as plasticizers for nitrocelluose and other resins which is not present for the lower, crystalline homologs. This application claims plasticized poly(vinyl chloride) and nitrocellulose compositions containing these cyclic hexahydrotriazines as plasticizers.

The overall process of this invention is illustrated by the following general equation:

NHgCOOR CHZO Polymer ROCON NCOOR N OR ' the reaction conditions.

In carrying out the process of this invention, the first step is the formation of the viscous, semi-solid products such as have heretofore been obtained by the reaction of carbamatcs with formaldehyde. These procedures have been described in U.S. Patent 2,171,965 noted above. Briefly, the process involves the reaction of an ester of carbamic acid with formaldehyde in the presence of an acid catalyst.

The ester of carbamic acid may be derived from any of a wide variety of alcohols having at least three carbon atoms. Thus, in the above formulae, R may be alkyl, including propyl, butyl, isobutyl, sec.-butyl, amyl, hexyl, heptyl, ethylhexyl, octyl, dodecyl, and the like, cycloalkyl such as cyclohexyl, cyclopentyl, methylcyclohexyl and the like, aralkyl such as benzyl and phenylethyl, and aromatic such as phenyl, tolyl, Xylyl and the like. The R groups may be also substituted with groups such as halogen, hydroxy, alkoxy and others which are inert under Where R is propyl, the corre sponding tris(carbalkoxy)-hexahydrotriazines may be prepared in poor yield directly from the reaction of propyl carbamate and formaldehyde; by the instant process, however, substantially improved yields are obtained. And when R contains four or more carbon atoms, the corresponding triazine was heretofore available by no known methods.

The formaldehyde reactant may be provided as aqueous formalin, or in other forms such as paraformaldehyde and trioxane. Usually a slight molar excess of formaldehyde is used.

The catalyst is about 5 to 10%, by weight of the carbarnate, of a strong acid. Mineral acids and acid salts are normally used, although the stronger organic acids are also effective. This mixture is refluxed for several hours, at temperatures under (1., to form the polymer. The polymer may be Washed free of acid, or residual acid may be retained for use in the next step. The polymer is dried for use in the next step Prolonged heating, or the use of larger amounts of acid, serve to increase the viscosity of the products. For use in the instant invention, the viscosity of the product formed at this stage is not critical. The products obtained are viscous hcmi-' colloidal oils or waxy solids, primarily linear in structure, having a viscosity in the range of about 10 to 2000 poises. A convenient viscosity product for use in the next step is in the range of about 50 to 100 poises.

In the next step, these linear polymeric products are degraded and rearranged to form monomeric cyclic hexahydrotriazines. This is accomplished by treating the polymeric product with an acid or acid-reacting catalyst in an anhydrous system for several hours at temperatures above 100 C.

The polymeric product may be dried by standard procedures, such as azeot-ropic distillation or stripping under educed pressure. In practice, this is conveniently done at (the end of the polymerization step, although water may also be distilled out of the system under the temperature conditions of the degradation step. The source of the water in the polymeric product is not only any water present in the reactants, but Water of reaction produced during the polymerization.

Suitable acid catalysts for the degradation include mineral acids such as sulfuric or phosphoric acid, strong orgaru'c acids such as acetic acid, chloroacetic acid, trichloroacetic acid, diglycolic acid, oxalic acid, alkyl and arylsulfonic acids, and the like, as well as such acid-reacting oatalysts as zinc chloride and aluminum chloride. In general, the stronger the acid, the more rapid and effective the cyclization reaction, and best results are generally obtained using mineral acids. It is preferable to use an acid which is not volatile under the reaction conditions, although acids such as hydrochloric or formic may be used under super-atmospheric pressure. About 1-10% by weight of acid catalyst is generally adequate to efiect the reaction, although there is no disadvantage to using larger amounts of acid. At very low acid concentrations or when using very weak acids the viscosity decrease is very slow, and complete reaction may not be obtained in a reasonable time. Residual acid from the first step of the process may be used to provide all or part of the acid necessary for carrying out the second step.

Temperatures over 100 C. are required for the degradation reaction, and best results are generally obtained between about 120 and 150 C. At temperatures below 100 C. the rearangemerit reaction is too slow to be practical. The upper temperature limitis controlled by the stability of theproduct, which tends to decompose in the presence of acid at elevated temperatures, resulting in color formation which may be difficult to remove. In the preferred temperature range a reasonably rapid reaction with little or no color formation is obtained, any color which may form being readily removed by subsequent carbon treatment.

If it is desired, for a particular use, to produce a product of intermediate viscosity, the degradation reaction may be stopped at the desired intermediate point, or smaller amounts of acid catalyst or weaker acid or lower temperatures may be employed to control the reaction. It is of interest to note that the degradation reaction does not occur during the initial reaction between the carbamate and formaldehyde, but only at the higher temperatures applied after the polymer has been formed.

'When the reaction is complete, or when the product viscosity has been brought to the desired value, the mixture is cooled, washed free of acid, and decolorized and distilled or otherwise purified if necessary. Standard procedures may be employed in working up the product.

As previously noted, the viscosity of the polymeric product formed from the initial condensation of the carbamate with formaldehyde is preferably in the range of about 50-100 poises, although the polymerization may be so carried out as to vary from 10 poises for lower alkyl groups to over 2000 poises. The subsequent rearrangement and degradation of the polymer results in a final product having a viscosity of about 1-5 poises for straight chain alkyl groups, and higher in the case of long. chain or branched chain alkyl and bulky R groups, usually up to about 10 poises. Where products of higher viscosity are desired for particular uses, mixtures of monomeric triazine and polymer may be prepared by this degradation reaction, to produce useful products having viscosities up to about 50 poises.

As previously stated the cyclic hexahydrotriazines of this invention are useful as plasticizers for poly(vinyl chloride) and nitrocellulose resins. The amount of plasticizer used will vary over a wide range depending upon the desired result. Improvement in processability of the resin can be achieved by using as little as about 5 parts of the hexahydrotriazine per 100 parts of resin. When the cyclic hexahydrotriazine is used as the sole plasticizer, the amount will preferably be in the range of about 50-100 parts of plasticizer per 100 parts of resin.

The following examples illustrate certain embodiments of the invention, and are not to be construed as limitative thereof:

Example I.-Preparati0n of 1,3,5-tris(carbobutoxy) hexahydro-s-triazine sure produced a forerun boiling up to 217 C., which partly crystallized on cooling. The crystalline material in this fraction was identified as N,N-methylene-bis- (butylcarbamate), M.P. 97-98 C. The main fraction was a colorless, odorless oil boiling at 217- 222 C. at 0.5 mm. The viscosity of this material was 1.4 poises at 25 C.; n 1.4672; 11 1.087. Infrared adsorption spectra and analysis of ionic fragments by the mass spectrometer confirm the hexahydro-s-triazine structure. Molar refnaction.Calcd for 1,3,5-tris(carbobutoxy)- hexahydros-triazine: 99.54. Found: 98.41.

Analysis.-Calcd for C H N G C, 55.79; H, 8,59; N, 10.85. Found: C, 56.16; H, 8.57; N, 10.71. Molecular weight (by mass -spectrometer)-Calcd: 387. Found: 387.

When 70 parts of this product was milled with 100 parts of poly(vinyl chloride) resin, a plasticized product having excellent oil resistance was obtained.

Example IL-Preparation of 1,3,5-tris(carbois0pefit0xy)- hexahydro-s-triazine Isoamyl carbamate, 131 parts, and 93 parts of 37% aqueous formaldehyde were acidified with 5 parts of 87% phosphoric acid in 50 parts of water and refluxed for two hours. The product was distilled free of water at 20 mm. pressure. The viscosity of the residual colorless material was greater than 100 poises at 25 C. On standing for several hours this material set up to a stiff paste. This residue was heated for two hours at 140- 150 C. After one hour the viscosity had dropped to 8.8 poises at 25 C. After two hours the viscosity was 7.2 poises. The product was treated with decolorizing carbon and filtered, to yield parts of a light-yellow colored oil, n 1.4544. An 80 part portion of this material was washed by agitation with hot water, dilute caustic, dilute sodium sulfite and finally several times with hot Water. The washed oil was freed of water by distillation and filtered, to give 73 parts of a yellowish oil having a viscosity of 6.25 poises at 25 C., 11 1.4650. Infrared analysis of this material showed it to consist primarily of 1,3 ,5 -tris (carboisopentoxy) -hcxahydro-s triazine.

Analysis.Calcd for C H N O C, 58.71; H, 9.14; N, 9.81. Found: C, 58.14; H, 9.20; N, 9.75.

When 50 parts of this product was milled with parts of poly(vinyl chloride) resin, a plasticized product having excellent oil'resistance was obtained.

Example III.-Preparation of 1,3,5-tris(carb0pent0xy)- hexahydro-s-triazine n-Amyl carbamate, 131 parts and 89 parts of 37% aqueous formaldehyde were acidified with 7 parts of 87% phosphoric acid and refluxed for two hours. The product was distilled free of Water at 20 mm. pressure. The residue was a colorless viscous balm. This material was then heated for a total of 3.5 hours at -150 C. After 15 minutes the viscosity was 17.5 poises at 25 C., after 30 minutes the viscosity had dropped to 2.75 poises at 25 C., after 1 hour the viscosity was 2.50 poises at 25 C., and after two hours the viscosity was 2.25 poises at 25 C. The product was carbon-treated and filtered, to give 100 parts of a yellowish oil. washed and dried as in the previous examples. The Washed product was a colorless and odorless oil having a viscosity of 1.65 poises at 25 C. and 11 1.4659. Infrared analysis of this product showed it to consist al- This material was most entirely of 1,3,5-tris(carbopentoxy)-hexahydro-striazine.

Analysis.C-alcd for C H N O C, 58.71; H, 9.14; N, 9.81. Found: C, 58.6; H, 9.27; N, 9.51.

When 70 parts of this product was milled with 100 parts of nitrocellulose resin, a plasticized product having excellent oil resistance was obtained.

Example IV.Preparatin 0 f 1 ,3,5-zris (carboocfoxy hexuhydro-s-triazine A mixture of 173 parts of n-octyl carbarnate and 89 parts of 37% formaldehyde was acidified with 7.5 parts of phosphoric acid in 50 parts of water and refluxed for 1.5 hours. After distilling the product free of water under 20 mm. pressure, the residue was found to be a very viscous paste. This material was heated at 140-l50 C. for a total of 3.5 hours. After minutes the viscosity of the product had fallen to 4.8 poises at 25 C. After 2.5 hours the viscosity was 3.2 poises at 25 C. At the end of 3.5 hours the product was treated with decolorizing carbon and filtered, to yield 125 parts of a yellowish oil having a viscosity of 2.9 poises at 25 C. This product was then washed and dried as in the previous eX- amples to yield a practically colorless oil having a viscosity of 2.4 poises at 25 C. and n 1.4645. The infrared absorption spectrum of this material showed it to consist principally of 1,3,5-tris(carbooctoxy)-hexahydros-triazine.

When 100 parts of this product was milled with 100 parts of nitrocellulose resin, a plasticized product having excellent oil resistance was obtained.

Example V .Preparation of 1,3,5-tris(carbo-2-erhyllzexoxy)-hexahydro-s-triazine A mixture of 400 parts of Z-ethylhexyl carbarnate and 180 parts of 44% formaldehyde was acidified with 12 parts of 87% phosphoric acid and refluxed for two hours. The organic layer which separated was removed, acidifled with 6 parts of phosphoric acid and dried by distillation at mm. pressure. The dried product was a viscous, colorless balm. This material was heated at 140- 150 C. for two hours. After 15 minutes the viscosity had decreased to 10.5 poises at C. After one hour the viscosity was five poises at 25 C. After two hours the product was cooled, carbon treated and filtered, to yield 410 parts of a practically colorless oil having a viscosity of 4.7 poises at 25 C. After washing and drying this material as in the previous examples there was obtained a colorless oil having a viscosity of 4.2 poises at 25 C. and H 1.4675. The infrared spectrum of this material showed it to consist almost entirely of 1,3,5-tris- (carbo-2-ethylhexoxy) -hexahydros-triazine.

Analysis.-Calcd for C H N O N, 7.56. Found: N, 7.29.

When 50 parts of this product was milled with 100 parts of nitrocellulose resin, at plasticized product having excellent oil resistance was obtained.

Example VI.Preparation of l,3,5-trz's(carbobutoxy)- hexahydro-s-triazine The effect of various acid catalysts was shown as follows: A mixture of 585 parts of n-butyl carbamate and 445 parts of 37% formaldehyde was acidified with 35 parts of 87% phosphoric acid and refluxed for 3.5 hours. The oil layer was removed and washed with hot water, dilute caustic, dilute sodium sulfite and finally several times with hot water. The washed, neutral product was dried by distillation, at a pressure of 2 mm. The residue partly solidified on cooling to form a thick, oily paste, having a viscosity of about 60 poises. A number of identical samples of this product were placed in test tubes immersed in an oil bath at 140-150 C. To each tube was added 0.25-05 gram of a variety of organic and inorganic acids and acid-reacting catalysts. An additional sample containing no catalyst was placed into the bath. After 2.5 hours the test tubes were removed from the bath and cooled to room temperature. All of the catalyzed samples had become completely liquid. Viscosities of these samples, measured at 25 C., were as follows:

Viscosity, Catalyst: poises Sulfuric acid 3.4 Diglycolic acid 17.0 Chloroacetic acid 3.5 Phosphoric acid 3.5 Zinc chloride 7.5 Aluminum chloride 4.0 Control 60 The uncatalyzed sample was an oily paste which was indistinguishable from the unheated product.

It is apparent that this invention is susceptible to numerous modifications within the scope of the disclosure, and it is intended to include such variations Within the scope of the following claims.

I claim:

1. A plasticized composition comprising poly(vinyl chloride) and, as plasticizer therefor, a 1,3,5-tris (carbalkoxy)-hexahydrotriazine wherein the alkyl group contains 4-12 carbon atoms.

2. A plasticized composition in accordance with claim 1 in which the 1,3,5-tris(carbalkoxy)-hexahydrotriazine is present in an amount of 50-100 parts per parts of poly(vinyl chloride).

3. A plasticized composition in accordance with claim 2 in which the alkyl group is butyl.

4. A plasticized composition comprising nitrocellulose and, as plasticizer therefor, a 1,3,5-tris(carballroxy)-hexahydrotriazine wherein the alkyl group contains 4-12 carbon atoms.

5. A plasticized composition in accordance with claim 4 in which the 1,3,5-tris(carbalkoxy)-he2rahydrotriazine is present in an amount of 50-100 parts per 100 parts of nitrocellulose.

6. A plasticized composition in accordance with claim 5 in which the alkyl group is butyl.

References Cited in the file of this patent UNITED STATES PATENTS 3,065,232 George Nov. 20, 1962 FOREIGN PATENTS 903,973 France Oct. 23, 1945 

4. A PLASTICIZED COMPOSITION COMPRISING NITROCELLULOSE AND, AS PLASTICIZER THEREFOR, A 1,3,5-TRIS-(CARBALKOXY) -HEXAHYDROTRIAZINE WHEREIN THE ALKYL GROUP CONTAINS 4-12 CARBON ATOMS. 